Surface composition of K3C60 multilayers and C60-3 monolayers investigated by high-resolution energy loss spectroscopy

High-resolution electron energy loss spectroscopy (HREELS) in reflection geometry was used to probe the surface of K3C60 multilayer films as well as CClick to view the MathML source monolayers adsorbed on Ag(111) and Cu(111). The −3 charge state of the adsorbed fullerenes was obtained by distilling K-saturated C60 monolayers. We found that roughly 2 electrons are donated by the K atoms on Ag(111) and slightly less than 1.5 electron in the case of Cu(111), the charge difference being provided by the metallic substrates. The surface of the K3C60 multilayer films has a charge state of about −1.5 and is thus underdoped.